/*
 * Licensed to the Apache Software Foundation (ASF) under one or more contributor license
 * agreements. See the NOTICE file distributed with this work for additional information regarding
 * copyright ownership. The ASF licenses this file to You under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the License. You may obtain a
 * copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
/*
 * Written by Doug Lea with assistance from members of JCP JSR-166 Expert Group and released to the
 * public domain, as explained at http://creativecommons.org/licenses/publicdomain
 */
/**
 * Misc utilities in JSR166 performance tests
 */

package org.apache.geode.internal.util.concurrent.cm;

import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;

class LoopHelpers {

  static final SimpleRandom staticRNG = new SimpleRandom();

  // Some mindless computation to do between synchronizations...

  /**
   * generates 32 bit pseudo-random numbers. Adapted from http://www.snippets.org
   */
  public static int compute1(int x) {
    int lo = 16807 * (x & 0xFFFF);
    int hi = 16807 * (x >>> 16);
    lo += (hi & 0x7FFF) << 16;
    if ((lo & 0x80000000) != 0) {
      lo &= 0x7fffffff;
      ++lo;
    }
    lo += hi >>> 15;
    if (lo == 0 || (lo & 0x80000000) != 0) {
      lo &= 0x7fffffff;
      ++lo;
    }
    return lo;
  }

  /**
   * Computes a linear congruential random number a random number of times.
   */
  public static int compute2(int x) {
    int loops = (x >>> 4) & 7;
    while (loops-- > 0) {
      x = (x * 2147483647) % 16807;
    }
    return x;
  }

  /**
   * Yet another random number generator
   */
  public static int compute3(int x) {
    int t = (x % 127773) * 16807 - (x / 127773) * 2836;
    return (t > 0) ? t : t + 0x7fffffff;
  }

  /**
   * Yet another random number generator
   */
  public static int compute4(int x) {
    return x * 134775813 + 1;
  }


  /**
   * Yet another random number generator
   */
  public static int compute5(int x) {
    return 36969 * (x & 65535) + (x >> 16);
  }

  /**
   * Marsaglia xorshift (1, 3, 10)
   */
  public static int compute6(int seed) {
    seed ^= seed << 1;
    seed ^= seed >>> 3;
    seed ^= (seed << 10);
    return seed;
  }

  /**
   * Marsaglia xorshift (6, 21, 7)
   */
  public static int compute7(int y) {
    y ^= y << 6;
    y ^= y >>> 21;
    y ^= (y << 7);
    return y;
  }


  /**
   * Marsaglia xorshift for longs
   */
  public static long compute8(long x) {
    x ^= x << 13;
    x ^= x >>> 7;
    x ^= (x << 17);
    return x;
  }

  public static class XorShift32Random {
    static final AtomicInteger seq = new AtomicInteger(8862213);
    int x = -1831433054;

    public XorShift32Random(int seed) {
      x = seed;
    }

    public XorShift32Random() {
      this((int) System.nanoTime() + seq.getAndAdd(129));
    }

    public int next() {
      x ^= x << 6;
      x ^= x >>> 21;
      x ^= (x << 7);
      return x;
    }
  }


  /** Multiplication-free RNG from Marsaglia "Xorshift RNGs" paper */
  public static class MarsagliaRandom {
    static final AtomicInteger seq = new AtomicInteger(3122688);
    int x;
    int y = 842502087;
    int z = -715159705;
    int w = 273326509;

    public MarsagliaRandom(int seed) {
      x = seed;
    }

    public MarsagliaRandom() {
      this((int) System.nanoTime() + seq.getAndAdd(129));
    }

    public int next() {
      int t = x ^ (x << 11);
      x = y;
      y = z;
      z = w;
      return w = (w ^ (w >>> 19) ^ (t ^ (t >>> 8)));
    }
  }

  /**
   * Unsynchronized version of java.util.Random algorithm.
   */
  public static class SimpleRandom {
    private static final long multiplier = 0x5DEECE66DL;
    private static final long addend = 0xBL;
    private static final long mask = (1L << 48) - 1;
    static final AtomicLong seq = new AtomicLong(-715159705);
    private long seed;

    SimpleRandom(long s) {
      seed = s;
    }

    SimpleRandom() {
      seed = System.nanoTime() + seq.getAndAdd(129);
    }

    public void setSeed(long s) {
      seed = s;
    }

    public int next() {
      long nextseed = (seed * multiplier + addend) & mask;
      seed = nextseed;
      return ((int) (nextseed >>> 17)) & 0x7FFFFFFF;
    }
  }

  public static class BarrierTimer implements Runnable {
    volatile boolean started;
    volatile long startTime;
    volatile long endTime;

    @Override
    public void run() {
      long t = System.nanoTime();
      if (!started) {
        started = true;
        startTime = t;
      } else
        endTime = t;
    }

    public void clear() {
      started = false;
    }

    public long getTime() {
      return endTime - startTime;
    }
  }

  public static String rightJustify(long n) {
    // There's probably a better way to do this...
    String field = "         ";
    String num = Long.toString(n);
    if (num.length() >= field.length())
      return num;
    StringBuffer b = new StringBuffer(field);
    b.replace(b.length() - num.length(), b.length(), num);
    return b.toString();
  }

}
